Verification Apparatus, Method of Controlling the Same, Storage Medium and Printing System Including the Verification Apparatus

1. A verification apparatus operable to (a) read a printed sheet to obtain a scanned image, and (b) perform verification processing for verifying whether there is an image defect in the printed sheet by comparing the scanned image and a correct image, the apparatus comprising: a first reader that reads the printed sheet to generate image data; a second reader that reads the printed sheet to generate image data, wherein respective items of the image data generated by the first reader and the image data generated by the second reader have an overlapping region in which they overlap; and one or more controllers including at least one processor and at least one memory, wherein the one or more controllers are configured to: (A) in generation of image data, (1) extract feature points of respective items of image data generated by reading the printed sheet with the first reader and image data generated by reading the printed sheet with the second reader; (2) determine whether any one of feature points of first image data generated by reading the printed sheet with the first reader corresponds to any one of feature points of second image data that should be generated by reading the printed sheet with the second reader; (3) in a case where it is determined in the determining that a first feature point of the feature points of the second image data corresponds to any one of the feature points of the first image data, convert coordinates of the first feature point from a coordinate system of the second reader to a coordinate system of the first reader; (4) in a case where it is determined in the determining that a second feature point of the feature points of the second image data does not correspond to any one of the feature points of the first image data, map coordinates of the second feature point on the coordinate system of the first reader; and (5) store coordinates of feature points of the second image data in the coordinate system of the first reader, and store the first image data and the second image data as the scanned image or the correct image; and (B) in the verification processing, (1) calculate a geometrical conversion parameter from (a) the correct image generated in the generation of image data and (b) coordinates of the feature points of the correct image and (c) the coordinates of feature points of the scanned image generated in the generation of image data; and (2) align the scanned image and the correct image based on the geometrical conversion parameter, and verify whether there is an image defect in the printed sheet.

2. The verification apparatus according to claim 1, wherein in the aligning of the scanned image data and the correct image, the scanned image and the correct image are aligned using an affine transformation with the geometrical conversion parameter.

3. The verification apparatus according to claim 1, wherein the one or more controllers are further configured to: in the verification processing, in a case where a difference for each pixel between the scanned image and the correct image is greater than or equal to a predetermined value, display that the printed sheet is defective.

4. A method of controlling a verification apparatus for (a) reading a printed sheet to obtain a scanned image, and (b) performing verification processing for verifying whether there is an image defect in the printed sheet by comparing the scanned image and a correct image, the method comprising: (A) reading the printed sheet to generate image data; (B) reading the printed sheet to generate image data, wherein respective items of the image data generated by the first reader and the image data generated by the second reader have an overlapping region in which they overlap; (C) in generation of image data: (1) extracting feature points of respective items of image data generated by reading the printed sheet with the first reader and image data generated by reading the printed sheet with the second reader; (2) determining whether or not each feature point of feature points of first image data generated by reading the printed sheet with the first reader corresponds to any one of feature points of second image data that should be generated by reading the printed sheet with the second reader; (3) in a case where it is determined in the determining that a first feature point of the feature points of the second image data corresponds to any one of the feature points of the first image data, converting coordinates of the first feature point from a coordinate system of the second reader to a coordinate system of the first reader; (4) in a case where it is determined in the determining that a second feature point of the feature points of the second image data does not correspond to any one of the feature points of the first image data, mapping coordinates of the second feature point on the coordinate system of the first reader; and (5) storing coordinates of feature points of the second image data in the coordinate system of the first reader, and storing the first image data and the second image data as the scanned image or the correct image; and (D) in the verification processing: (1) calculating a geometrical conversion parameter from (a) the correct image generated in the generation of image data and (b) coordinates of the feature points of the correct image and (c) the coordinates of feature points of the scanned image generated in the generation of image data; and (2) aligning the scanned image and the correct image based on the geometrical conversion parameter, and verifying whether there is an image defect in the printed sheet.

5. A non-transitory computer-readable storage medium storing a program for causing a processor to execute a method of controlling a verification apparatus for (a) reading a printed sheet to obtain a scanned image, and (b) performing verification processing for verifying whether there is an image defect in the printed sheet by comparing the scanned image and a correct image, the method comprising: (A) reading the printed sheet to generate image data; (B) reading the printed sheet to generate image data, wherein respective items of the image data generated by the first reader and the image data generated by the second reader have an overlapping region in which they overlap; (C) in generation of image data: (1) extracting feature points of respective items of image data generated by reading the printed sheet with the first reader and image data generated by reading the printed sheet with the second reader; (2) determining whether or not each feature point of feature points of first image data generated by reading the printed sheet with the first reader corresponds to any one of feature points of second image data that should be generated by reading the printed sheet with the second reader; (3) in a case where it is determined in the determining that a first feature point of the feature points of the second image data corresponds to any one of the feature points of the first image data, converting coordinates of the first feature point from a coordinate system of the second reader to a coordinate system of the first reader; (4) in a case where it is determined in the determining that a second feature point of the feature points of the second image data does not correspond to any one of the feature points of the first image data, mapping coordinates of the second feature point on the coordinate system of the first reader; and (5) storing coordinates feature points of the second image data in the coordinate system of the first reader, and storing the first image data and the second image data as the scanned image or the correct image; and (D) in the verification processing: (1) calculating a geometrical conversion parameter from (a) the correct image generated in the generation of image data and (b) coordinates of the feature points of the correct image and (c) the coordinates of feature points of the scanned image generated in the generation of image data; and (2) aligning the scanned image and the correct image based on the geometrical conversion parameter, and verifying whether there is an image defect in the printed sheet.

6. The verification apparatus according to claim 1, wherein the one or more controllers are configured to use another geometrical conversion parameter other than the calculated geometrical conversion parameter in the mapping of the coordinates of the second feature point on the coordinate system of the first reader.

7. The verification apparatus according to claim 1, wherein the another geometrical conversion parameter is generated in advance using a chart image and is stored in the one or more controllers.